1. Field of the Invention
The present invention relates to a method of manufacturing a silicon carbide semiconductor device.
2. Description of the Related Art
US 2003/0013266 A (corresponding to JP 2003-69012 A) discloses a silicon carbide (SiC) semiconductor device, in which a face A having a (11-20) crystal face orientation is used as a channel. The SiC semiconductor device has a MOS (metal-oxide semiconductor) structure, and a channel mobility is improved by hydrogen anneal or being treated in a wet atmosphere that includes both of a hydrogen (H) atom and an oxygen (O) atom. Specifically, the channel mobility is improved by controlling a concentration or a temperature of the hydrogen anneal or the wet atmosphere.
However, further channel mobility is required for the SiC semiconductor device. US 2007/0045631 A (corresponding to JP 2007-96263 A) by the inventors of the present application discloses that a termination/desorption temperature is determined based on the wet atmosphere or a hydrogen atmosphere. The termination/desorption temperature is a temperature at which a dangling bond between SiC and a gate oxide layer is terminated by an element of hydrogen (H) or hydroxyl (OH), i.e., a temperature at which H or OH desorbs. Specifically, the desorption of H or OH mainly occurs at a temperature about in a range between 800° C. and 900° C., and the termination of the dangling bond by H or OH also occurs in the same temperature range. Therefore, the termination/desorption temperature is about in the range between 800° C. and 900° C. Thus, it is required for keeping the wet atmosphere or the hydrogen atmosphere until the temperature decreases at about 800° C. or lower, preferably at about 700° C. or lower, to terminate the dangling bond by H or OH.
When a heating process is performed in the wet atmosphere, an interlayer insulation layer made of BPSG (boron phosphorus silicon glass), for example, absorbs moisture, thereby a material of an electrode disposed on the interlayer insulation layer may be corroded. Thus, it is required to restrict the material of the electrode from being corroded by moisture included in the interlayer insulation layer.